Steel forging is a key metalworking method in the manufacturing process and is widely used in the production of various industrial components. However, in the process of steel forging, there may be some defects, which will affect the quality and performance of the final product. Although these defects are not widely discussed because forging companies are reluctant to draw attention to these issues, understanding these defects is still very important to ensure the reliability and performance of
forgings.
Forging defect is usually defined as a state in which product characteristics deviate from expected specifications. While some defects may not exceed what is allowed in the specification and therefore are not considered serious defects, close attention is still needed to ensure product quality. These defects can originate from a variety of factors, including the quality of raw materials, operational problems during forging, mold design, or improper post-forging treatment.
Here are some common and uncommon steel forging defects in actual closed die forging operations, as well as their causes and potential solutions.
Unfilled part refers to the forging process, the forging fails to completely fill the mold, resulting in incomplete product shape or size does not meet the design requirements. This defect is usually caused by poor mold design leading to poor material flow, or insufficient raw materials, uneven heating and other reasons. To solve this problem, it is necessary to optimize the mold design so that it can effectively guide the metal flow and ensure the integrity of the filling; At the same time, the supply of materials and heating time are reasonably controlled to ensure that raw materials are sufficiently heated and softened to smoothly fill the mold.
Cold close refers to the small cracks or creases that appear on the forging, usually occurring in the corners or edges of the product. This defect is usually caused by the presence of sharp corners or sharp edges in the mold design, resulting in stress concentration, and the mold or forging cooling rate is too fast. In order to avoid cold closure, it is necessary to increase the radius of the rounded corner of the mold to reduce the stress concentration point, and adjust the cooling speed appropriately to avoid cracks inside the material caused by too fast cooling.
Scale pit is a surface defect that appears as irregular pits or rough areas on the forging surface, usually caused by insufficient cleaning of the forging surface, or oxides and contaminants in the forging environment attached to the forging surface. This defect is common in open forging environments. By thoroughly cleaning the surface of the forgings before and after forging, and conducting the forging operation in a closed and controlled environment, the formation of scale pits can be effectively prevented.
Die misalignment refers to the failure of the upper die and the lower die to align properly during forging, resulting in a deviation in the size and shape of the forging. This situation is mostly caused by the equipment adjustment is not in place or the mold installation is not correct. In order to avoid this defect, it is necessary to add positioning notches on the mold to ensure that the upper and lower molds can be accurately aligned in every operation, while regularly checking and maintaining the forging equipment to ensure that it is always in a good alignment state.
Sheet cracks are small cracks formed inside forgings, usually caused by sharp temperature changes during the cooling of forgings. This defect is commonly seen in the case of rapid cooling, which will reduce the overall strength and toughness of the forging. In order to avoid cracks in the sheet, the technology of controlling the cooling rate should be used to ensure that the forging is gradually and evenly cooled, reduce the difference in internal and external temperature, and reduce the generation of internal stress.
Improper grain growth refers to the metal grain structure of the forging does not match the expected, which may lead to a decrease in the mechanical properties of the material. This defect is usually caused by poor flow or uneven cooling of the metal during forging. In order to prevent improper grain growth, the mold design should be optimized to ensure the smooth flow of the metal during the forging process, and the cooling speed is controlled during the cooling process to obtain a uniform grain structure.
Incomplete forging penetration means that the forging fails to reach the required forging depth or strength, usually due to insufficient forging force or too fast hammering speed. This defect will cause the internal structure of the forging to be uneven, which will affect its mechanical properties. To solve this problem, the force and hammering speed of the forging press need to be properly adjusted to ensure that the forging is evenly and fully forged throughout the process.
Surface cracking refers to the small cracks on the surface of the forging, usually occurring in low-temperature forging operations, due to the increased brittleness of the material under low temperature conditions, it is easy to crack. To avoid surface cracking, it is necessary to forge within the appropriate temperature range, avoid operating at temperatures where the material is vulnerable to embrittlement, and ensure that the material is preheated to a sufficient temperature before forging to reduce stress concentration and the risk of cracking on its surface.
Residual stress refers to the internal stress residual caused by uneven or too fast cooling speed during forging and cooling. This stress may cause deformation or cracking of forgings and affect their performance. In order to reduce the generation of residual stress, a gradual slow cooling process should be used to make the temperature difference between the inside and outside of the forging as small as possible, so as to reduce the accumulation of internal stress and maintain the size and structural stability of the forging.
These are the most common types of defects in steel forging, and their appearance can significantly affect the quality and performance of forgings. Therefore, we need to understand the causes and prevention methods of these defects, improve the forging process and improve product quality. For any production needs or questions about forged steel products, please contact CT Forging Company in China, we will provide you with professional advice and solutions.
